Visual acuity is a primary concern for both the patient and the healthcare professional. Proper measurement of visual acuity is of paramount importance in detecting disease of the visual system and should be included in every general physical exam. Unfortunately, visual acuity remains one of the least monitored parameters of health in the healthcare community. J. H. Sheldrick et al. published a study entitled "Study of diagnostic accord between general practitioners and an ophthalmologist" in volume 304, pp. 1096-8 of the 1992 British Medical Journal. Of 1103 patients who visited a general physician with an eye complaint, visual acuity was recorded in the medical record for only 114 of the patients. This low visual acuity testing rate of approximately 10% occurred in spite of the fact that the study questionnaire specifically asked the general physician if visual acuity was assessed.
P. Shah et al. published a study entitled "Measurement of visual acuity by hospital physicians" in volume 69(813), p. 595 of the 1993 Postgraduate Medical Journal (England). In that study, 102 hospital physicians were asked four basic questions about testing visual acuity, and only 24.5% of the doctors answered all four questions correctly. Ninety-three percent could name the distance visual acuity chart, known as the Snellen chart. Seventy percent knew that the correct distance of twenty feet should be used between the chart and the patient. Fifty-six percent knew how to obtain a rough estimate of visual acuity if the patient did not have their spectacle correction available. Only 63% were able to correctly record the visual acuity of a highlighted line on a Snellen chart pictured in the questionnaire.
The Sheldrick study and the Shah study raise questions of why visual acuity is tested so infrequently by the general physician and why so little is known about how to do it properly. First and foremost, the proper measurement of visual acuity is a time-consuming process. If healthcare professionals were given a faster, more convenient, more reliable, and more portable way to test visual acuity, the visual acuity testing rate would increase dramatically. Second, healthcare providers must be educated concerning the importance of screening their patients for decreased visual acuity. As healthcare reform proceeds, primary healthcare providers will assume more and more responsibility for determining when their patients need to be referred to an eyecare specialist, and therefore will have a greater responsibility to test the visual acuity of their patients.
While the Snellen chart has long been the standard for testing vision in the office, the Rosenbaum Pocket Vision Screener has been the standard for testing vision in emergency rooms and hospitals. The Rosenbaum Pocket Vision Screener and other similar pocket-sized near vision testers consist of thin cards, approximately 6.25 inches by 3.5 inches by 0.04 inch, made of plastic, cardboard, or laminated cardboard. Near vision test objects consisting of numbers, letters, pictures, or symbols of different sizes are arranged in rows on the front face of these pocket-sized near vision test cards. The largest sized test objects are located in the top row of the card with progressively smaller test objects arranged in rows proceeding down the card.
The near vision test is performed by holding the near vision test card 13 to 16 inches from the patient's eyes, depending on which style of near vision test card is being used. The patient's left eye is covered and the patient is asked to read the smallest line possible with his or her right eye. Then, the patient's right eye is covered and the patient is asked to read the smallest row possible with his or her left eye. While holding the card, the examiner is positioned to the side of the patient in order that: a) the patient may be monitored for proper fixation and occlusion, and b) the front face of the test card may be monitored for the correctness of test responses.
Given their thinness and rectangular shape, pocket near vision testers are easily carried in the pocket of a healthcare professional's coat. This pocket-sized portability affords the healthcare professional a much easier means of testing vision in acute or chronically ill patients than could ever be achieved by using the bulkier Snellen chaff at a distance of 20 feet. Other pocket vision testers, such as Reese, U.S. Pat. No. 686,535 and Costenbader, U.S. Pat. No. 2,573,546, use test disks that are dialed manually by the examiner to bring various near vision test objects into view. However, these testers are awkward to use and did not achieve much commercial success.
Near vision test cards also may be used in the eyecare professional's office where they can be removably mounted on the protruding reading card rod of a phoropter. A phoropter is an ophthalmic refracting apparatus which is typically mounted on an adjustable arm next to the patient examining chair. The protruding reading card rod of the phoropter is ruled in inches and centimeters and has a sliding attachment means for removably securing near vision test cards. The phoropter has many different optical lenses that allow the examiner to assess a patient's refractive error. The patient's distance refractive error is the sum total and orientation of lens power needed to focus the patient's vision at twenty feet or more. The patient's near refractive error is the sum total and orientation of lens power needed to focus the patient's vision at fourteen inches. Once appropriate lenses are in place to focus the patient's vision at or near fourteen inches, a near vision test card is attached to the protruding reading card rod of the phoropter, and the card is positioned to refine this focus and to measure the best corrected near visual acuity.
A significant problem in using a near vision test card on a phoropter is the lack of satisfactory illumination of the test card. Currently, the majority of eyecare professionals use external lighting sources located on hinged positioning arms. These lamps must be positioned by the examiner for each patient, and therefore require time and effort to set up. The end result is an amount of light striking the near vision test card which is by no means standardized or reproducible. Potter, U.S. Pat. No. 2,282,494, and Blenkle, U.S. Pat. No. 5,220,362, attempted to address this problem. However, given their bulky design, these external illumination systems are not suited for portable use in hospitals and emergency rooms.
In the field of visual acuity testing, there are many large office or desktop-sized near and distance vision testing devices, such as described in patents by Griffin et al., U.S. Pat. No. 4,740,072, Waltuck et al., U.S. Pat. No. 5,121,981, and Jovicevic, U.S. Pat. No. 5,129,720 as well as in the Soviet Journal of Optical Technology (March 1976) by Gassovskii et al. These devices are used to test the visual acuity of persons who can be positioned at a testing station. They are not easily transported by healthcare professionals from one hospital room or emergency room to the next. There are also many different kinds of projector-type vision testing devices that are used to test distance visual acuity in the office setting. These devices are even less easily portable than the desk-top models. The size of these desk-top and projector-type vision testing devices severely limits their use in hospitals and emergency rooms in that acute or chronically ill patients would have to be seated at a test station to have their vision tested.
It is much easier to use a hand-held, lightweight, pocket vision test card with acute or chronically ill patients. These test cards, as described above, are positioned in front of the patient's eye without changing the patient's position. However, in many clinical situations, there are numerous practical difficulties in using these cards at the bedside or chairside. First, the pocket near vision test cards in present use are not illuminated. If inadequate illumination is available, the patient must be moved to an area of better illumination, or a source of illumination must be directed on the card (usually a penlight from the examiner's pocket). The use of a penlight occupies one of the examiner's hands that he might need to perform other tasks associated with near vision testing. Second, the patient's attention span often is decreased because of illness or injury, and the examiner must somehow direct and maintain the patient's attention on the section of the card being used. This is usually accomplished by the examiner placing his or her thumb below the row in question thereby occluding the row below and forming an incomplete frame of the row in question. The penlight is then focused on the row or test object in question and the patient is asked to read the row or identify the test object. Many eyecare professionals use brightly colored felt-tip pens to draw frames around the individual rows or test objects that they use to test cognitively or speech-impaired patients. Alternatively, a second health worker may point at the desired row or test object while the examiner holds the card and directs the penlight. Third, if the patient is unable to cover his or her own eye, a patch must be applied or another hand must be used to cover the eye. Fourth, if the patient is unable to open the eye to be tested, the eye must be opened with the examiner's fingers or with some sort of mechanical eyelid retractor. In the case of the severely swollen eye (such as seen in severe trauma, infection, tumors, or inflammatory disorders), the eyelids must be gently pried apart with two hams operating two separate eyelid retractors. Finally, the card must be held by someone (preferably the examiner) at the correct distance and in the proper orientation.
In the worst case scenario (a patient with decreased mental status, one severely swollen eye, and unable to use his or her own hams), the examiner might need a total of six hands: (1) one to hold the card, (2) one to hold the penlight, (3) one to direct the attention of the patient to the proper section or individual test object on the card, (4) one to cover the untested eye, and (5-6) two to open the swollen eye. This invention allows the healthcare professional to perform the first four tasks listed above without an assistant.